Knowledge of Fact and knowledge of the Cause must be distinguished, and even within the same Science.[41] In some syllogisms the conclusion only brings out [Greek: to\ o(/ti]--the reality of certain facts; in others, it ends in [Greek: to\ dio/ti]--the affirmation of a cause, or of the _Why_. The syllogism of the _Why_ is, where the middle term is not merely the cause, but the proximate cause, of the conclusion. Often, however, the effect is more notorious, so that we employ it as middle term, and conclude from it to its reciprocating cause; in which case our syllogism is only of the [Greek: o(/ti]; and so it is also when we employ as middle term a cause not proximate but remote, concluding from that to the effect.[42] Sometimes the syllogisms of the [Greek: o(/ti] may fall under one science, those of the [Greek: dio/ti] under another, namely, in the case where one science is subordinate to another, as optics to geometry, and harmonics to arithmetic; the facts of optics and harmonics belonging to sense and observation, the causes thereof to mathematical reasoning. It may happen, then, that a man knows [Greek: to\ dio/ti] well, but is comparatively ignorant [Greek: tou= o(/ti]: the geometer may have paid little attention to optical facts.[43] Cognition of the [Greek: dio/ti] is the maximum, the perfection, of all cognition; and this, comprising arithmetical and geometrical theorems, is almost always attained by syllogisms in the First figure. This figure is the most truly scientific of the three; the other two figures depend upon it for expansion and condensation. It is, besides, the only one in which universal affirmative conclusions can be obtained; for in the Second figure we get only negative conclusions; in the Third, only particular. Accordingly, propositions declaring Essence or Definition, obtained only through universal affirmative conclusions, are yielded in none but the First figure.[44] [Footnote 41: Ibid. I. xiii. p. 77, a. 22 seq.] [Footnote 42: Themistius, p. 45: [Greek: polla/kis sumbai/nei kai\ a)ntistre/phein a)llê/lois to\ ai)tion kai\ to\ sêmei=on kai\ a)/mphô dei/knusthai di' a)llê/lôn, dia\ tou= sêmei/ou me\n ô(s to\ o(/ti, dia\ thate/rou de\ ô(s to\ dio/ti.] "Cum enim vera demonstratio, id est [Greek: tou= dio/ti], fiat per causam proximam, consequens est, ut demonstratio vel per effectum proximum, vel per causam remotam, sit demonstratio [Greek: tou= o(/ti]" (Julius Pacius, Comm. p. 422). M. Barthélemy St. Hilaire observes (Note, p. 82):--"La cause éloignée non immédiate, donne un syllogisme dans la seconde figure.--Il est vrai qu'Aristote n'appelle cause que la cause immédiate; et que la cause éloignée n'est pas pour lui une véritable cause." See in Schol. p. 188, a. 19, the explanation given by Alexander of the syllogism [Greek: tou= dio/ti].]